Trifluoroiodomethane (CF3I) is a useful compound in commercial applications, as a refrigerant or a fire suppression agent, for example. Trifluoroiodomethane is an environmentally acceptable compound with a low global warming potential and a low ozone depletion potential. Trifluoroiodomethane can replace more environmentally damaging materials.
Methods of preparing trifluoroiodomethane from trifluoroacetic acid and elemental iodine are known. For example, Kyong-Hwan Lee et al., “Synthesis of CF3I by Direct Iodination of CF3COOH on Solid Catalyst,” discloses a vapor phase reaction of TFA and I2 to produce CF3I. TFA liquid is metered into a three-necked flask containing iodine and heated to vaporize the iodine. Together, the TFA and iodine vapors flow to a reactor charged with a solid catalyst. The output of the reactor flows into a heated collector, and then through a heated line, to a second collector. The vapor stream including the CF3I flows through a basic solution to neutralize acids. Thus, Lee discloses a batch process, with a fixed quantity of I2 vaporized together with a fixed quantity of TFA. Lee discloses that catalysts with activated carbon are better than alumina.
U.S. Pat. No. 8,722,945 to Yang et al. discloses a vapor phase reaction of a precursor, such as TFA, with a source of iodine, such as I2, to produce a fluoroiodoalkane, such as CF3I. The process may be a batch process or a continuous process. The patent discloses methods for pretreating a solid catalyst and regenerating the solid catalyst. The solid catalyst may include an alkali metal, an alkaline earth metal, transition metals, lanthanides or rare earth metals, including various metal salts. The solid catalyst may be supported on an activated carbon substrate.
U.S. Pat. No. 8,8871,986 to Yang et al. discloses a vapor phase reaction of a precursor, such as TFA, with a source of iodine, such as I2, to produce CF3I. The process may be a batch process or a continuous process. The patent discloses various catalyst promoters to promote catalyst activity and stability. The catalysts include alkaline metals, alkaline earth metals, and salts thereof supported by a carbonaceous carrier. Non-carbonaceous carriers may also be employed.
U.S. Pat. No. 8,034,985 to Yang et al. discloses a vapor phase reaction of a precursor, such as TFA, with a source of iodine, such as I2, to produce a fluoroiodoalkane, such as CF3I. The patent discloses various catalysts including d1s1 and/or lanthanide elements. The catalysts can be used in bulk or supported by activated carbon. Non-carbonaceous carriers may also be employed.
The above references generally describe the use of activated carbon as a catalyst support. While activated carbon catalysts may afford excellent selectivity to producing CF3I, they are susceptible to rapid deactivation as coke deposits accumulate on the catalyst surface, decreasing the effective surface area of the catalyst. In some cases, oxygen gas is co-fed with the reactants to simultaneously remove the deposits by oxidation. However, the oxygen gas may also lead to progressive reduction in the quantity of carbon in the catalyst as the carbon in the catalyst combusts during the reaction. The loss of carbon may adversely impact the activity of the catalyst.
Thus, there is a need to develop a more durable catalyst along with an efficient process that may be scaled to produce commercial quantities of trifluoroiodomethane.